Formate

Formate (IUPAC name: methanoate) is the conjugate base of formic acid. Formate is an anion (HCO−
2) or its derivatives such as ester of formic acid. The salts and esters are generally colorless.[1]

## Contents

* 1 Fundamentals
* 2 Biochemistry
* 3 Formate esters
* 4 Formate salts
* 5 Examples
* 6 References

## Fundamentals

When dissolved in water, formic acid converts to formate:

HCO
2H → HCO−
2 \+ H+

Formate is a planar anion. The two oxygen atoms are equivalent and bear a partial negative charge. The remaining C-H bond is not acidic.

## Biochemistry

Formate is a common C-1 source in living systems. It is formed from many precursors including choline, serine, and sarcosine. It provides a C-1 source in the biosynthesis of some nucleic acids. Formate (or formic acid) is invoked as a leaving group in the demethylation of some sterols.[2] These conversions are catalyzed by aromatase enzymes using O2 as the oxidant. Specific conversions include testosterone to estradiol and androstenedione to estrone.[3]

Formate is reversibly oxidized by the enzyme formate dehydrogenase from Desulfovibrio gigas:[4]

HCO−
2 → CO
2 \+ H+
\+ 2 e−

## Formate esters

Formate esters have the formula HCOOR (alternative way of writing formula ROC(O)H or RO2CH). Many form spontaneously when alcohols dissolve in formic acid; contrariwise, they hydrolyze easily in base.[5]: 674, 682 Some formate esters arise by the addition of formic acid to alkenes.[6]

An important formate ester is methyl formate, which is produced as an intermediate en route to formic acid. Methanol and carbon monoxide react in the presence of a strong base, such as sodium methoxide:[1]

3OH + CO → HCOOCH

Hydrolysis of methyl formate gives formic acid and regenerates methanol:

HCOOCH
3 → HCOOH + CH
3OH.

In laboratory, formate esters can be used to produce pure carbon monoxide.[7]

Reaction with phosphorus pentachloride does not chlorolyze the ester bond, instead forming an (unusual) dichloromethyl ether.[5]: 684

Formate esters often are fragrant or have distinctive odors. Compared to the more common acetate esters, formate esters are less commonly used commercially because they are less stable.[8] Ethyl formate is found in some confectionaries.[1]

## Formate salts

Copper(II) formate hydrate

Formate salts have the formula M(O2CH)(H2O)x. Such salts are prone to decarboxylation. For example, hydrated nickel formate decarboxylates at about 200 °C with reduction of the Ni2+ to finely powdered nickel metal:

Ni(HCO

2(H
2O)
2 → Ni + 2 CO
2 \+ 2 H
2O + H

Such fine powders are useful as hydrogenation catalysts.[1]

## Examples

* ethyl formate, CH3CH2(HCOO)
* sodium formate, Na(HCOO)
* potassium formate, K(HCOO)
* caesium formate, Cs(HCOO); see Caesium: Petroleum exploration
* methyl formate, CH3(HCOO)
* methyl chloroformate, CH3OCOCl
* triethyl orthoformate
* trimethyl orthoformate, C4H10O3
* phenyl formate HCOOC6H5
* amyl formate

## References

1. ↑ 1.0 1.1 1.2 1.3 Reutemann, Werner; Kieczka, Heinz (2000), "Formic Acid", Ullmann's Encyclopedia of Industrial Chemistry, doi:10.1002/14356007.a12_013, ISBN 3-527-30673-0
2. ↑ Pietzke, Matthias; Meiser, Johannes; Vazquez, Alexei (2020). "Formate Metabolism in Health and Disease". Molecular Metabolism 33: 23–37. doi:10.1016/j.molmet.2019.05.012. PMID 31402327.
3. ↑ Lephart, E. D. (1996). "A Review of Brain Aromatase Cytochrome P450". Brain Res. Rev. 22 (1): 1–26. doi:10.1016/0165-0173(96)00002-1. PMID 8871783.
4. ↑ Reda, Torsten; Plugge, Caroline M.; Abram, Nerilie J.; Hirst, Judy (2008). "Reversible interconversion of carbon dioxide and formate by an electroactive enzyme". Proceedings of the National Academy of Sciences 105 (31): 10654–10658. doi:10.1073/pnas.0801290105. PMID 18667702. Bibcode: 2008PNAS..10510654R.
5. ↑ 5.0 5.1 Gibson, Harry W.. "The chemistry of formic acid and its simple derivatives". Chemical Reviews. doi:10.1021/cr60261a005.
6. ↑ Kleinfelter, Donald C.; Schleyer, Paul von R. (1962). "2-Norbornanone". Org. Synth. 42: 79. doi:10.15227/orgsyn.042.0079.
7. ↑ Imberdis, Arnaud; Lefèvre, Guillaume; Cantat, Thibault (2019). "Transition-Metal-Free Acceptorless Decarbonylation of Formic Acid Enabled by a Liquid Chemical-Looping Strategy". Angewandte Chemie International Edition 58 (48): 17215–17219. doi:10.1002/anie.201909039. PMID 31529586. https://cea.hal.science/cea-02290859.
8. ↑ Panten, Johannes; Surburg, Horst (2015), "Flavors and Fragrances, 2. Aliphatic Compounds", Ullmann's Encyclopedia of Industrial Chemistry, pp. 1–55, doi:10.1002/14356007.t11_t01, ISBN 978-3-527-30673-2

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